The present invention relates to a semiconductor circuit device having a step-down circuit, and more particularly to a semiconductor circuit device having a switched capacitor type step-down circuit, and further to a semiconductor circuit device having a switched capacitor type step-down circuit and a series regulator type step-down circuit, involving for instance a technique effectively applicable to a microcomputer for a portable communication terminal device or a system-on-chip semiconductor circuit device (system LSI).
On-chip step-down circuits for semiconductor circuit devices include series regulator type step-down circuits. As a series regulator type step-down circuit steps down the voltage by the turning-on resistance of a transistor, as much power is lost as the voltage is stepped down. More efficient arrangements than series type circuits in power conversion include switching regulator type step-down circuits (FIG. 1 in Patent Reference 2). As a switching regulator type step-down circuit requires an inductor as an external unit, it entails problems in mounting space and cost. Step-down circuits needing no inductor and yet excelling in power conversion efficiency include switched capacitor type step-down circuits (FIG. 9 in Reference 2). Further, FIG. 1 in Patent Reference 1 illustrates a circuit configuration in which a switched capacitor type step-down circuit is connected to a series regulator type step-down circuit in series, and a stepped-down voltage supplied from the series regulator type step-down circuit is received and further stepped down by a switched capacitor type step-down circuit.
[Patent Reference 1] Japanese Unexamined Patent Publication No. 2002-325431
[Patent Reference 2] Japanese Unexamined Patent Publication No. 2002-369552